Fringe office arrangement



Jan. 10, 1950 R. E. HERSEY FRINGE OFFICE ARRANGEMENT l5 Sheets-Sheet 1Filed April 25, 1945 lNl/ENTOR R. E. HERSEV ATTORNEY Jan. 10, 1950 R EHERSEY 2,494,475

FRINGE OFFICE ARRANGEMENT Filed April 25, 1945 15 Sheets-Sheet 2REHERSEV,

awn um llvl/ENTOR R. E HE RSE V ATTORNEY l5 Shets-Sheet 3 R E HERSEYFRINGE OFFICE ARRANGEMENT asp/av" DNMVNIWHEL Jan. 10, 1950 Filed April25, 1945 15 Sheets Sheet 4 I lNVENTOR R. E. HERSEV BY 1 ATTORNEY.

R E HERSEY FRINGE OFFICE ARRANGEMENT Filed April 25, 1945 w 9 1 0 l n hJan. W, 1950 R. E. HERSEY 2,494,475

FRINGE OFFICE ARRANGEMENT Filed April 25, 1945 15 Sheets-Sheet 5INVENTOR R. E. HE RSE Y c. flzm ATTORNEY Jan. 10, 1950 R. E. HERSEYFRINGE OFFICE ARRANGEMENT Filed April 25, 1945 15 Sheets-Sheet 6 3S 3&1?mung F AES mes lNl ENTOR R. EHERSEY a. aw

ATTORNEY 15 Shets-Sheet 7 Filed April 25, 1945 INVENTOP R EHERSEY C./%4/ZZZ(.

ATTORNEY Jan. 10, 1950 R. E. HERSEY FRINGE OFFICE ARRANGEMENT l5Sheets-Sheet 8 Filed April 25, .1945

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INVENTOR By REHERSEY C. /wdzzu.

ATTORNEY NQQ . Q 9k QQQTQE Jan. 10, 1950 R. E. HERSEY' FRINGE OFFICEARRANGEMENT 15 Sheets-Shget 9 Filed April 25, 1945 ATTORNEY Jan. 10,1950 R. E. HERSEY FRINGE OFFICE ARRANGEMENT Filed April 25, 1945 15Sheets-Sheet 10 v INl ENTOA R. 5 HERSEY 6. hum;

ATTORNEY Jan. 10, 1950 R. E. HERSEY FRINGE OFFICE ARRANGEMENT l5Sheets-Sheet 11 Filed April 25, 1945.

V, v. Mm M 6 a: S wti Jan. 10, 1950 R. E. HERSEY FRINGE QFFI CEARRANGEMENT Filed April 25, 1945 15 Sheets-Sheet l2 ATTORNEY Jan. 10,1950 R. E. HERSEY FRINGE OFFICE ARRANGEMENT l5 Sheets-Sheet 13 Filed.April 25, 1945 #REEEEB as afimlom INVENTOR R. E HERSEV 8V (2. hid/mt;

ATTORNEY Jan. 10, 1950 R. E. HERSEY FRINGE OFFICE ARRANGEMENT FiledApril 25, 1945,

15 Sheets-Sheet 14 INVENTOR R EHERSE) L. hum/v A r Tom/Ev Jan. 10, 1950R. E. HERSEY FRINGE OFFICE ARRANGEMENT 15Sheets-Sheet 15 Filed April 25,1945 INVENTOR R. E. HERSEV A TTORNE Y Patented Jan. 10, 1950 FRINGEOFFICE ARRANGEMENT Ralph E. Hersey, Madison, N..J., assignor to BellTelephone Laboratories, Incorporated, New York, N. Y., a corporation ofNew York Application April 25, 1945, Serial N0. 590,260

This invention relates to telephone systems and has for its object tofacilitate the establishment of interoffice connections.

It frequently occurs that small towns on the outskirts of a metropolitanarea have such community of interest that the telephone service requiredis very largely local in character. It is therefore possible to providesuch local service by means of comparatively simple dial switchingequipment and to place all interoflice service under the control oftandem equipment located within the metropolitan area.

In accordance with the present invention, in such a local ofiiceemploying cross bar type dial switching equipment, means is providedunder the control of a key at the substation for automaticallyconnecting the calling line with a trunk to a tandem ofiice.

More specifically, the tandem key when operated connects ground throughthe ringer to the tip conductor of the line and when the line has beenextended to the control circuit or sender, means responsive to thisground serves to automatically connect the line with a trunk outgoing tothe tandem equipment and to release the sender. The ground detectingmeans prevents the transmission of dial tone from the local sender.

According to the preferred form of the invention the ground detectingmeans in the sender returns a signal to the sender link control circuitwhich wipes out the selection of the district junctor and causes thecontrol circuit to test for and extend the calling line to an idle trunkto the tandem ofiice.

According to an alternative form of the invention the ground detectingmeans of the sender ciated with the subset of the tip party on 'a party14 Claims. Cl. 179-18) line, Fig. 2 showing the equipment normal andFig. 3 with the grounding contact locked;

Figs. 4 and 5 show in detail the equipment associated with the subset ofthe ring party on a party line, Fig. 4 showing the equipment. normal andFig. 5 with the grounding cam locked;

Fig. 6 is a diagrammatic showing of the equipment and circuits at thetip party substation;

Fig. 7 is a diagrammatic showing of the equip- ,ment and circuits at thering party substation;

Figs. 8 to 20 show the circuits employed in con necting a. calling linewith a sender, a district incoming link and a tandem trunk;

Fig. 8 showing a calling subscribers line, a line a link and, thehorizontal group circuit;

Fig. 9 showing parts of a district junctor circuit and a tandem trunkcircuit, together with a schematic showing of terminating and tandemequipment;

Figs. 10, 11, 14, 1'7 and 20 showing the line link control circuit;Figs. 12, 13, 15, 16 and 18 showing a sender link and the sender linkcontrol circuit;

Fig. 19 showing parts of a sender circuit; and

Fig. 21 shows the manner in which Figs. 8 to 20 inclusive, should bearranged for an understanding ofthe invention.

For convenience the present invention has been disclosed as applied tothe line and sender links and control circuits as disclosed and claimedin United States Patent 2,224,251, granted December 10, 1940 to A. J.Busch and E. L. Erwin, and in general the same reference numerals havebeen used.

As described in the above-identified patent, the standard cross bar lineswitch arrangement employs primary line switches having ten sets ofvertical contacts which are connected to sub+ scribers lines and tensets of horizontal contacts which are connected to line links. Thehorizontal contacts may be multiplied together so that one set of tenline links may serve as many as seventy lines. The other ends of theline links are connected to horizontal contacts in the secondary lineswitches. District junctors are connected tothe sets of verticalcontacts in the secondary line switch.

district junctors. In the establishment of a connection to a tandemtrunk, the subscriber connects ground to the tip conductor in the mannerdescribed hereinafter. In response to the removal of the receiver orhandset, the line is connected to an idle district junctor and idlesender in the manner described in the above-identified patent and aswill be described hereinafter. The sender tests for this ground and,finding it present, prevents the connection of dial tone to the line andthe locking of the sender to the line. The ground detecting means thenreleases the district. junctor. test relays, opens the district junctor.test. leads, closes the tandem trunk test leads and causes the districtjunctor test relays to test for an idle tandem trunk, after which the:

vice, for both local and tandem calls, the localsender is arranged totest for a grounded tip con-- ductor as soon as seized to determinewhether a local or tandem connection is desired and again following thedialing of the first digit. to. determine which party is calling, andthe substations are provided. with special. dial. controlledmeans forapplyingthe tip party. ground. This will be apparent from thedescription of Figs. 1 to Timelusive.

Fig. 1 shows a stand or desk mounting. I for a handset .I 9!, showninsection. The handset controls a plunger lllziwhich acts upon a.lever I93mounted on a bracket Hi4; This lever isso formed as to control the usualswitchhook contacts I as well as a cam Ilfiassociatedwith the dialassembly. Seated in a recess in the face of. the stand It!!! is a.casing. I96 containing the. dial mechanism. The shaft carrying the dialcams and the finger. wheel IIl'I. also carries an eccentric. cam Hit. Abracket ID9,'attached in any suitable man-- her to the standififisupports, insulatedly, a pair of spring contact members III! and II I.. Two means are shown for operatingcontact member. I II intoengagement with member III, one of which is tandem. key HZ WhiCh ismountedby. means of a plate I26 secured to the stand. I'flil adjacentthe dial Hi6. and carries a stud. I I3which has a cammingaction onspring I I I3. The second means is a follower II I, suitably'pivoted onbracket I09, on which are arranged a roller I I 5 anda stud I I1. Key IIZis of thewell-known' locking type, having a locking cam I21 which isarranged to lock under locking plate I28. This plate" isresilientlyattached to plate I25 and has a trippingarm I30,

held in position by" spring I 3i anchored toan arm I29. of bracket. I89.The cam member I I5, previously mentioned, is slidablymounted on bracketHi9 and has an arm II 3 which extends under a latching member I I9.

In order to more clearly indicate the manner in which the apparatus ofFig; 1 functions, reference maybe made to Figs; 2, 3 and 6. With-thehandset in the cradle, cam; H6 is. pressed forwardso that latch .I I9 israised on the. camming surface of arm H8, stud I .II is held back by'theaction of spring IZEonfolIoWer llfland'key- I I2 and stud I I3 are heldelevated by-spring Hi.

If the subscriber having. this. equipment wishes to make a local call heremoves his handset and waits. for. dialitone. The. removal of'thehandset permits. cam..i.i.6 tobe drawn back under. the com trol ofspring I22 (Fig. 1) tothe positionshown in.Fig. 3. Latchllddrops ontothe. top of spring II!) but is-inefiectiVe. As shown in.Fig..6,the.re-,lease of .cam I I5 permits-the .closureoftheswitchhook contactsrepresented by contact I23, thereby establishing a direct currentclosure across the line conductors I24 and I25 to initiate the operationof the line link control circuit as described 5 hereinafter. It is to beunderstood that the handset IGI, dial I06 and contact I23 are intendedto represent a conventional subscribers substation, only thesupplementary equipment being shown in detail.

When dial tone is heard, the subscriber operates the dial. As soon asthe dial is moved oil normal for the first digit, cam I58 rotates withthe dial, acting throughroller I I5and follower I II to press stud. II"! against spring IIII. Spring I Ii], moving along the camming edge oflatch H9 lifts that latch which drops behind the spring looking it inplace, as shown in Fig. 3, in contact with spring HI where it remainsthroughout the call. The eiiect of theclosure ofthe contact betweensprings go H9. and I I I' is to connect ground through ringer I34directlyto, the tip conductor I24 and through the subset to the ringconductor I25 to identify the calling substation as the tip party on aparty line.

If the subscriber haddesired to make a tandem call,.. he would. .have.depressed key I.I2.,, before removing: the receiver, whereupon keystudwould have moved spring IID'into contact lwithvspring II I. Atthesame time, locking cam. IZ'I, would pass. through theopeningin'locking plate I28 and latch, underjit. to hold. the key in theposition .shown inFig. 3. The removaloi the, receiver er-- mits latchIIS to fallinto the-locking position. The operation ofthe dialcausescamI08'to move stud. llljl'"'against spring Ii 0' but. since that spring isalready locked in place the dial is inefiective to operate the spring IIII.

Following either. type oi call, the. replacement of. the; handset. I0].inthe cradle. advances cam I I6 40 -.so that. the. cammi-ng surfaceonarm II 8 liitslatch I] 9. If. spring. IQIII. is locked. only by latchH9, it.immedia.te1y returns to normal; If key IIZ has also been locked,tongue I32 whichis pivotally mounted on.latch IIH, presses againsttripping arm. I30. to moveplate I28. oii cam. I2] and unlock key I .I2-. Bin. I 33 limitsthe motion. oftongue I32 to render. it effectiveonly during the lifting ofdatch H9.

Figs. 4,5, and .7 show the equipment at the sub.- station. .of .a. ring.party on. a. party. line. The equipmentis substantially the same as thatshown for the. tip party, except that. the. follower II-i carries, inplace of the stud III, a longer arm on which is. mounteda-roller I35.The actionin response toremoving the handset is the same as for. thetip. party. When the tandem key is op.- erated the contactbetweensprings H0. and III is closed andlocked. as described. In, this case,however, whenthe subscriber dials, the cam I08, iiOacting throughfollower II4 on. roller I35, lifts latch I19 restoring tandemkey II 2.and the spring Ill)- Therefore. there is no ground on the lineconductors Inland I25 when the sender makes its second test...following.the dialing of the first digit. the,..c.ase of alocal call, the actionof the dial cam I08 causes roller I35 to lift latch H9 ateach turnof thedial,.but since the spring I It has notbeen. operated, the action isineiiective.

Theioregoingdescription of the-equipment at 7.0 the substriberssubstations willclarify the operation of the circuits .as nowtraced.

Start of originating call- When the. subscriber at substation which ismay be assumed'to. be. the same as that shown in anon-14m Fig. 6;initiates. a local: call-,;, the. removali ofnthe receiver from theswitchhook-zoperates.line-relay' 1 86 .over a; circuit frombattery,vthrough thee/vinding of.- relay 166;.outer:breakgcontact-of hold magnetE04, through-the substation circuit, inner break contact of mag-net-164*?130 ground-.1 Relay 106 in operating; servesato, seize! thelinelilak.v con-v trol circuit and to identify the calling line to thecontrol circuit. To'thisend; relay ice: grounds individual lead 12.4and.commonstartleadlfi. The. start circuit closedoyerconductor'i'i'd'maybe. traced. from ground over the armature and make. contact of. relayi136; conductor. 125,. left-J hand contacts of, relay i into a,iuncti'on'pointon conductor lZT; thence overone. branch through.

a break contact ofrelay THL-TcOnd'uctOr li'fljright, outer .loreakcontact .of .gaterelay l2 3,; conductor 125', to the Windingoffstartrelay. T293, and'iover. the otherbranoh through abreak'contact'of'relayTH}, conductor. 536; right outer. break;.con-tact of gate relay HS;conductor, T31. tothe-wi'nding, of. start relay'ilfi.

Relay- 72!], energizes the. masterstart. relay 805 in. a circuitextending froinbattery on a.. break contact of relay lfll'5,conductorlilii, windingaof relay 8&5, conductor 814; right. outenbreakcon: tacts of relay 8'i3',.conductor 815, contactof relay; 8B1,conductor. 8 l E,"contact.of a. relay in. the mate frame. circuit, notshown, conductor. 9l3',.. break. contact of jack. N365, conductor H322,right. inner make contact of relay 12H, conductor. T32, break contact.864. ofrelay 8%,. conductor. 819,, break. contact of continuity springs3.51 onrelayfilil, conductor 82B, breakcontactof relay] 5; break.contact of key HHS; toground. Similarly, relay H6" energizes relay 8M.Relay 894,.however, is made slow operating so that, although it isenergized at the same instant relay 8ii'5,.its operation will'undernormal conditions be prevented by the speedier movement-of the latterrelay. Relay are locks to conductor 8i 5 inde.-.. pendent of relay filii'and the mate controlcircuitt and operates relay 8 l IS. Thecircuitfor' relay; 811}: extends frombattery on conductor .813, Windingof relay" 8%; conductor 83.0,; through the mate frame circuit to:conductor 916, .left'iouter make contact -ofrelay" iii-35;] conductor83%; left inner, breakcontact of relay Bil-8, conductors-.81? and 8 itto ground as above traced.

Relay Blfl operates the controlconnector-tee lays to bring intensethe-linkcontrolcircuitof Figs. 1? and 29. Control connec-tor relay mil-Ioperatesin a circuitfrombattery'at a break contact o1"- relay ifilE;over'conrlucton [t -26 of relaylilizi, conductor-[621 a -right front contact of relay E18, conductor 83%; toground at a break contact ofrel'easerelay l-fil'm 'in the control circuit. Relay 132i locks itselfWithgrounclfrom its own front contact, over conductoriilZ-t, makecontacts of relay Bill in series, conductor: [021, backzto its ownwinding; Control connector ree lays IEBI 1263,: not and Hit also.operate. and lock under the. control ofrelay Silt:

Control connectorrelay 8.9 21,; operates gate: relay 123111 acircuitffrom battery, windingrofi relay 123, conductor 134%; to, ground.at;a make contact Ofrel'ay [32L Relaywfitslocks:oyerxcone ductor: 735"to, groundsat a. make .contactiofi relay. 805, and opensithe: operatingpaths:;:oithestarir relays, T28, et.c-., but the startgrelaylfiltremainse locked'to the start. lead: independent .of relay 1 -23;; Withrelay i283 operated, asupplementary-locke ingpath for relay 72s isprovided over conductor 136, break contact of. relay- 8%, conductor839,,

Bit.

groundthrough, the.-,--winding;s-oi relaydillllr and also;to...d-irec-t. ground over; conductorr HHS. and theilower. break.contact; of relay 16.! 4'.-

The horizontal group: relay Hi9.- corresponding 1 to the preferred startrelay: 1-20; is-,now operated from groundsupplied by; relay 12-3. This;circuit may be tracedfrom battery, winding of h0rizontal grouprelay-Hi9;conductor 137;. left outer make; contactof relay 129,conductor MIL- amake -contact of relay I213; conductor 122i, left outerbreak contact of. relay 808, conductor'lM, left outer make contact. ofrelay 123, to ground. The tenli-nelinks accessible tozthe horizontal"group represented'by relay Hi9 are noW put in readiness by 1 theoperation of their secondary select triage nets; Relay l tfi closesthese paths, one of which may be: traced" frombattery, Winding of. line.link secondary select mag-nets l2, and 1 Min. parallel; conductor 151-,makewcontact of-relay'llw, con,

.ductor lES, to ground at the break'contact: of the make-bus5t jackAlso.- variousindividual leads: pertaining to the. horizontal groupareconnected through the-makesprings of relaylfiil to correspondingcommon leads.

In thisway, the sevenstart leads 125-, etc.,.associated, respectively;with. the seven. ten-line groups; composing the maximum horizontalgroup, are. connected over. a corresponding'number of common leads,through the control connector re- .lays to the control circuit, and soto the windings;

respectively, of. theseven chainrelays represented by relays I591, seenand 1563-. These sevenrelays serve to-make a-recordof Whatever ones-ofthe seven ten line groupsare attempting to: originate calls. atthemoment; and by their chain'arrange ment give preference to thelowestnumbered group; Allseven orthe-relays 55. 31, etcz, operateinitially, since,'thersevenstart leads 1-25," etc: are; for the timebeing,;tiedjtogether at break contacts of relay H0; The path foroperating'relay IEM maybe tracedfrom battery, winding of relay l5ili:;..conductor-llilfi, up er. inner breakccntaot of-relay' i598,"conductor r53 9, left inner. make contact: of. control connector relay l251! l, conductor U 1223, a makecontact ofrelay lull, conductor- 742',

start'leadi 125, toground attheleft make contact of; line relay-1H5; Allother ,relays'oithe chainsuch as I502, etc., operate oyer asimilar path,through the left break contacts of relay'ilfland .themultiple point onlead 12:1, to start lead E25.

Relays .150 l etc. each close apathfrom ground, through their.upper-outer make contacts, conductor l52l, bottom-outer break springs ofrelay l-5li9,; conductor H522, to the winding of relay H513, andbattery, operating. that relay. Relay [El-3 completesv a pathforoperating relay lElAr in, aseries circuit carried throughmake.--.contacts of the. seven relays i l-ill, etc. soas to check, theoperation: of the latter relays. This circuitmay be traced frombattery-through the Winding. of relay I614; conductor 5M9, outer lowermake contactsofrelays-l5E3, i582, I5ill; etc, conductor I524, make,contact of relay lei- 3, conductor i623, make contact of relay l2 l3,conductor me, make. contact, ofrelay 'llia conductor l-Zl, break con-.-tact of relay 'Hliato: groundon-,.start conductor 125,. Relay lei-4. inoperating removes r und from, conductor i518 to" open the shunt aroundrelay lfili l; grounds a -path for. operating relay,

i HlLand-closes a locking. path for itsclf'in series- Wi-th. relay i535.Relay .6565 remains. normal for the moment, since its winding. isshunted by. the ground: present. on; conductor is ill.

Relay :TLB .upon operating opensethe "operating ma-kecontact of. relayL103; conductor 12% 1 texts: nathsrfor-relays H5. andfl2fl, restoringtheformer 1 and leaving the latter locked in series with relay I504.Relay I504 with its second shunt removed in this manner, now operates inseries with relay I20. Relay 'lI0 also separates the seven start leadsfrom each other, thus removing ground from the start leads of allnon-calling tensgroups and restoring the corresponding chain relaysI50I, etc. The chain relays corresponding to calling tens-groups remainoperated, and they lock themselves in obvious manner around the breakcontacts of relay I500 through which their respective operating circuitspass. Relay I I also removes ground from the operating circuit of relayI5I4. The shunt is thus removed from around relay I505, which nowoperates in the locking circuit of relay IBM. Relay I565 closes thecircuit for operating gate relay I560, in a path extending from battery,Winding of relay I500, right outer make contact of relay I505, conductorI527, make contacts of relay I50I to the start ground used for operatingrelay I50I.

Selection of the tensroup first to be served is governed by the seriesWiring on chain relays I50I, etc. Preference is given to the lowestnumbered group and the selection is completed by operating thecorresponding line connector relays I01 and 708, a pair of which arefurnished for each tens-group in the horizontal group. The operatingcircuit for this pair of relays is closed by relay i500, the path beingtraced from battery, windings of relays I07 and I08 in parallel,conductor I44, a make contact of relay I09, lead I 45, right makecontact of relay I203, conductor I226, make contact of upper transfersprings on relays I50I, etc., the chain circuit wired through thesetransfer springs, conductor I525, make contact of relay I500, conductorI526, lower middle make contact of relay I500 to ground.

Connection is thus established between the selected tens-group and thecontrol circuit in preparation for the next step, namely that ofrecording the calling lines in the group and of selecting the line to beserved. Relay I08 connects the individual contacts of the ten linerelays I06 over make contacts of connector relay "HI and break contactsof gate relay I5I0 to the windings, respectively, of the ten controlcircuit relays represented by I5II, I5i2, etc. As many of the ten relaysI51 I, etc. operate as there are lines calling, and the lowest numberedrelay in the group operates relay I508 in a circuit from battery,winding of relay I508, conductor I530, lower inner series chain circuitand make contact of relay i5, etc., conductor I529, to conductor I035and ground over the operating circuit of relay I5II. Relay I508 closesthe operating circult of relay I507 from ground on the conductor I030used in operating relay I5II, etc., locking contact of relay I5I I,upper inner series chain, conductor I53 I lower outer make contact ofrelay I508, winding of relay I501, to battery. Relay I 507 locks itselfthrough its right inner make contact and its right middle make contact,conductor I534, left outer make contact of relay I288, to ground. Thislocking ground for relay I507 is passed back over conductors I532 andI53I to lock relay I5I I and the same ground is also carried through theright middle double make contact of relay I501, over conductor I535,winding of relay IE? to battery, operating the latter relay. Relay I5I0serves to release all relays in the group of higher number than therelay locked as already described. The selection of the line to beserved has now been accomplished, since this line is the one whose holdmagnet derives its energizing path from the only one of the chain relaysI5I I, etc. left operated.

Relay I50! connects ground from its left middle make contact overconductor I 536 to lock relay I500 and the operated chain relay I50I,etc. At this time the calling line ceases to control disconnection ofthe link control circuit.

District group test and selection While the operations of selecting,recording and connecting to the calling line are still under way, stepsare taken to select a group of ten district incoming junctors which areaccessible to the line link. The line link control circuit first makesan availability test on the basis of groups of ten district junctors, todetermine how many such groups: (a) contain each at least two idledistrict junctors, (b) have their sender link control circuit availableat the moment, (0) have at least one path available from the callingline through line link, district junctor, and sender link, to a sendergroup containing an idle sender. District junctor groups not meeting allthese requirements are disregarded at this time The line link circuitsignifies a preference for one of the available ten-junctor groups byoperating a lock-out relay corresponding to the twenty-junctor groupwhich contains the preferred ten-junctor group. This lock-out relayexcludes other line link con trol circuits and connects the line linkcontrol circuit in question to a portion of the common control leadswhich are associated with the twentyjunctor group and which, on the onehand, are multiplied throughout all line link frames served by thattwenty-junctor group, and on the other hand, terminate at the senderlink frame where the junctor group terminates. Over these leads a signalis passed to the sender link control circuit telling it that a call iswaiting on the twentyjunctor group, and this group receives service ifit is in preferential relation to other twenty-junctor groups which mayat the same moment be attempting to place calls from other line linkframes. A signal of acceptance is then returned from the sender linkover the common leads above-mentioned, to the line link control circuit.The line link control circuit thereupon definitely selects thetwenty-junctor group and next, the particular ten-junctor group to beused, employing for this purpose certain connector relays to establishconnection with additional ones of the common control leads associatedwith the twenty-junctor group. The choice as to the ten-junctor group issignaled from the line link control circuit to the sender link controlcircuit, and the latter circuit proceeds to select the individualdistrict junctor, sender link, and sender, as will be described later.

The test for availability of paths begins with the operation of relay109, since this relay closes test paths from the sleeves of the ten linelinks to the windings of the ten relays represented by relays I6I5 andI6I6. One such path may be traced from battery, winding of relay I615,conductor I626, a make contact of relay I02I, conductor "13!, upperlever spring and break contact of jack I, conductor MI, make contact ofrelay I09, conductor to sleeve conductor 15L The sleeve conductors areheld busy by connection to ground, as will be explained, so that thepresence of ground on the sleeve will operate the corresponding relayI6I5, etc., and the latter relay by opening the operating paths of itsassociated relay I509, etc., will indicate that the line link isenenemas spondto the five groups of twenty district junctors whichrespectively extend, under ordinary wiring arrangements, to fivedifferent district link frames-and their-associated sender link frames.

The operating path for relay I609 runs from battery, through thewinding'of relay I609, by way of conductor l62'l, upper inner makecontact of relay I6I3, conductor I 628, upper break contact of relayI6I5,conductor-I629, upper inner break contact of relay I 6 I I,conductor I630, a'm'ake con-1,

tact of relay I02I, conductor "I032, upper inner break contact of relayI204, common-conductor I228,-'upper'break contactof relay I603,conductor I8I8, lower outer break contact ofrelay I8I3,

conductor I8 I9, lower outer break contact of jack I8I2, conductor I820,upper inner break contact of relay I'II l, conductor I'II6,-breakcontact of sender link-holdmagnet I105 to ground.

'As pointed out in the previously-identified Busch eta1. patent, theoperation-of relay I609 indicates (a) that for the corresponding-groupof ten district junctors the sender'link-providing access to thatgroup'is available for use, (b) that the group of ten districtjunctorsin question containsat least two junctors-availableior use, (c)J that thesender link is available for use (d) that for the group oftendistrict'junctors inquestion' at least one sender link path isavailableand (e) that the group of senders to which this link pathconnects-is non-busy or in other words, has at least'on'e of its sendersavailable.

Having determined through the operation of relays I609, -I6I0, etc.,which groups often district junctors are ahle'to'serv'e the'calLthe linelink control circuit expresses a preference by operating lockout relayI2 I8. The energizing path for relay I2I-8 may be traced 'from'ground,over "a chain circuit involving the upper breakcontacts of relays I2I6and I2I'I, respectively, winding of relay I2-I8,'conductor I23 l,'-amake contact of relay 'I02I, conductor I033, make contact of left middletransfer springs on relay I'600,assumed operated, conductor-I63I, breakcontact of left middle transfer springs on relay I6I2, conductor I632,jumper between cross-connection blocks,

I608 and I604, conductor I633, lovverbreak-con tact on relay I603,conductor I63 I,*rig'l"it inner make contact onrelayI505,'resistanceI506 to battery. Relays I'2I8', etc., not only act aslook out relays, but they serve also asconnector relays" to connecttheir respective line link frames to some of the common controlleadspertaining to the twenty-'district'gr'oup; I

Withthe operation of relay I2I8, the line link frame is able-to signalover the common control leads to the sender link frame and demandservice on the twenty-district junctor'group. Relay I6I3 connects groundfrom its lower outer armature and front contact, over conductor I635,make contact'on relay I2 I3, conductor "I 235, contact'of relay I'2I8,multiple'strap I233, conductor 1232, make contact of key I009, normallyoperated, conductor I92 I ,-windingoi start relay I9I2, series chainthrough c'ontinuitycontacts 'of'r'elays I 9 I3 and I'9I4,series chainthrough lower inner break 10 springs or relays I901, I906, 1505 andrent, to battery at the bottoni break springsof relay I908. The startrelays represented by relays 'I9'I2, I9'I-3 and 19 M are five'in number,one each for the five groups o'f twen ty district -junctors*served bythe-sender nk'fra me. Assuming relay I9I'2 to be the meter relay -itlocks to battery on its right inner make springs and closes ground fromits left outer arm'ature and make contact; over conductor I92'4,-acontact of key l909gnormally operated, conduct-or I925, winding ofrelay-ll I3, to battery. Having grant-ed preference toa particular groupcf-jtwe'ntydi'strict j-u'n'ctors, the sender link circuit signalsaccordingly to the line link circuit attached to that-district junctorgroup. The

ground used for this purposeis the paths available'ground already tracedwhich extends to'con ductor l 320,thence by conductor II Il, through amake "contacto'f relay Hi3, overconductor III8,

a-contact of key =I909, conductor I026, break contact of way-2p I0,"conductor 2035, a make contact or key I909, conductor I921, a mak'econtact of relay III-3, conductor I 'II 9, lower armatureandm'ake'contact'of relay I2I0, conductor I231, makec'ontact of relay I2i 3 conductor I238, lower outer armature "and break spring of relayI603,

conductor I 6 3ljthe jumper between the terminal blocks I60 l'ahd'I606,conductor I633, chain circuit on right inner armature and breakcontact of relay I6I2, conductor I639, tothe lock armature and windingof relay I609, and battery. From conductor I238 a branch conductor I636carries emu-new the winding of relay I6I'I, and

battery. Relay'l609 locks operated, while relay I 6I'I operates andopens the operating paths of all of the'relays I669, I610, -tc.,-thusrestoring all except-thelocked one. Relay I6I'I connects ground-'fromitslower mak'e'contact over conductor I6 I6,'winclingof relay I5I5, tobattery, operating-the latter'relay. Relay I5I5 closes a circuitfrom'ground at the left inner make contact of relay I501, conductorI539, upper inner make contact'of relay I5I5, conductor I540, lowerinner armature and break contact ofrelay I603, conductor -I64I, crossconnection between terminal block's I604 and I608,*to the chain circuitat-the leftouter transfer springs of relay I612, conductor I642,leftouter armature and make contact of relay I*6 00, conductor I643, amake contact 'of-relay' I02 I c'onductor I 034, upper make contact of'relay' I2I 8, conductor I239, winding of relay I2II, and battery.ReIayIZII, like relay I2I8,'isrepresentative of thepreferred group-oftwenty district juncto'rs and its operation completes the processof'selectin'g the twenty-group. Relay "I2I'I also-closes additionalcontrol leads for the selected 'junctorgr'oup, and completes'theoperatingpaths for relays I209 and I2I0, which represent "respectivelythe first and second ten district junctors in the twenty-group. Relay I209'will be the'ohe' to'operate, since it isassumed that thefirst one inthe pair of test relays I609 and I6I'0 islocked operated.

Relay I209 now operates the primary select magnets of the line link,since the choice of the district tens-group determines the'ter'rninatingor secondary end of the linelink, the circuit for primary select magnetI05 extending from battery through the winding of thatmag'net, makecontact of relay I09, conductor'i56, upper inner make contact of relay I-1200, conductor I243, a make contact of relay I2I3, conductor I244 toground at a break contact of release relay I509. Relay I209 alsonotifies the sender link astotlie'choice' of the district tens-group,with ground from its

